Method of making seamless tubes



J. L. ,MAUTHE 2,227,313

METHOD OF MAKING SEAMLESS TUBES Filed Aug. 19, 1958 2 Sheets-Sheet 1 Fi'JA.

INVENTOR James L. Mau 1'he R1351 M MIM Dec. 31,1940. J MAUTHE 42,227,313

METHOD OF MAKING SEAMLESS TUBES Filed Aug. 19, 1938 2 SheetsSheet 2lNVENTOR Jam es LMau fh e Jamm MMJM Patented Dec. 31, 1940 UNITED STATESPATENT OFFICE James L. -Mauthe, Poland, Ohio, assignor to The YoungstownSheet and Tube Company, Youngstown, Ohio, a corporation of OhioApplication August 19, 1938, Serial No. 225,749

4 Claims.

This invention relates to the manufacture of seamless pipe or tubes and,particularly, the making of such tubes having relatively largediameters, viz., 4 to 18", and relatively thin walls.

It has been the practice heretofore inmaking seamless tubes, to heat abillet of such size as to produce a single commercial length of tube,subjeot it to successive piercing operations and then plug rolling,followed by reeling, cross rolling if desired and sizing. In thepractice of the method outlined, furthermore, it has been customary toeffect a certain-amount of work in the piercing operations and a largeamount of work in the plug mill. Numerous disadvantages characterize themethod described but it has continued in-use. for lack of anythingbetter. The heavy reductions effected in the plug mill prevent theproduction of a good surface inside the tubes. A further objection isthat the inner and outer surfaces of pierced billets cool at differentrates, the outside cooling more rapidly since it is exposed to theatmosphere and also because the work done on the billet in piercing isconverted into heat which serves to maintain or elevate the temperatureof the inner surface. This differential cooling, in some sizes andgrades of steel, causes cracking and a rough surface condition. It hasbeen attempted in the past to overcome these effects by cooling theinner surface with a steam spray. This, however, is expensive and notsubject to accurate control.

A further disadvantage of the prior method lies in the fact that thebillets employed for making tubes of many commercial lengths are tooshort to be handled in a walking beam furnace, for the reason thateiiicient heating in such furnaces requires a definite minimum spacinbetween the supporting beams.

I have invented a novel method and apparatus which overcomes theaforementioned objections and is characterized by further novel featuresand advantages over the existing practice. Accordingto the preferredprocedure, I heat multiple length billets by passing them through afurnace of the walking beam type and then sever them into individualbillets for further processing. The individual billets are subjected toan initial piercing and then reheated in a suitable furnace. They arethen subjected to a second piercing operation during which a heavyreduction is effected. After the second piercing, the pierced shells areagain reheated and plug rolled before reeling and sizing. If theindividual bili5 lets ar long enough to be handled on a walking beamfurnace, it is unnecessary to .pass them therethrough in multiplelengths. Any or all the operations after the second piercing operation,furthermore, may be omitted.

A detailed description of the method of my in- 5 vention and apparatussuitable for carrying it out will be given by referring to theaccompanying drawings. In the drawings:

Figs. 1a and 1b when disposed side by side with the former on the left,constitute diagrammatic illustrations partly in plan and partly insection, of a seamless tube plant.

Referring now in detail to the drawings, billet heating furnaces ID ofthe walking beam type are disposed side by side and each is providedwith a pusher ll adapted to eject billets therefrom onto a conveyor l2disposed between the furnaces. The structural details of the furnacesthemselves require no description since they are well known. They arepreferably provided with 0 automatic control means whereby billetscharged thereinto are progressively advanced toward the discharge endand thereby heated to the proper temperature. As already stated, if thebillet for making a single commercial length of the char- 25 acter oftube to be manufactured is too short to be handled by the walking beamsof the furnace, I charge multiple length billets intothe furnace, i. e.,billets which are small integral multiples of (two or three times) thelength of 30 the billet required for making a single tube of the desiredcommercial length.

After passing through the furnaces ll), billets are discharged(preferably alternately from the two furnaces) onto the conveyor l2.They are 35 then shifted to a conveyor 13 by means of pivoted transferbars I and skids l5. The heated billet is advanced by means of theconveyor l3 to a billet cutter. indicated schematically at l6. If thebilletis of multiple length, it is here severed 0 into individuallengths. I prefer to employ a hot billet cutter, i. e., one which seversthe billet by means of a gas flame, although a hot saw or other billetsevering means may also be employed. After the cutting of amultiple'length billet. the leading portion thereof is advanced to aposition beside a centering device I! and transferred thereinto byrotatably mounted arms Hi. If the billets are long enough in singlelength to be handled by the walking beam furnaces, they are advanceddirectly to the centering device without stopping at the cutter IS. Thecentering device l1 preferably includes a torch for burning a hOle inthe end of the billet to facilitate starting of the first piercingoperation, A mechanical centering mechanism may be used, however, ifdesired. After centering, the billet is discharged across skids I9 ontoa conveyor 20. It is then shifted by rotatable arms 2| onto skids 22 bywhich it is delivered onto the inlet table of the first piercing millindicated diagrammatically at 23. After piercing of the billet, theresulting shell is moved from the outlet table 24 across skids 25 ontothe conveyor 20.

A reheating furnace 28 overlies the portion of the conveyor 20 beyondthe skids 25. The furnace may be of any desired structure and is adaptedto prepare the pierced shell for the substantial reduction to beeffected in the second piercing or expanding operation. The furnacetemperature is preferably between 1900 and 2400" F. The reheating of thepierced shell after the first piercing operation has several importantdesirable results. In the first place, the cutting of multiple lengthbillets allows the outer ends of the billets exposed to the atmosphereto be cooled to a temperature slightly below that of the severed ends ofthe billet which have been cut by the cutting torch. This temperaturedifference would hinder easy working of the steel to uniform dimensionsif not corrected before too much work is completed. That is to say, thehotter end of the billet being more plastic than the cooler end, wouldbe reduced more than the latter, thus producing a shell having a taperinwall thickness. This is substantially eliminated by the reheating afterthe initial piercing because the temperature throughout the shell isthereby made substantially uniform. A more important result is thatreheating after the first piercing prevents the differential between thetemperatures at the inner and outer surfaces of the shell mentionedabove and thus precludes the cracking and rough surface conditionpreviously encountered. Reheating after the first pierping, furthermore,permits a heavy reduction in the second piercing operation. The furnace26 also serves to restore to the second portion of a multiple lengthbillet the heat lost thereby while waiting for the first portion to becentered and advanced to the first piercer, before the second portioncan be similarly treated. This furnace also equalizes the temperaturethroughout the material and overcomes the unequal cooling caused by thehead end of the pierced shell passing over a water cooled mandrel whilethe rear end of the piece is being pierced.

The furnace 2B is preferably constructed for sidewise discharge ofshells therefrom onto skids 21 by rotatable arms 28. From the skids 21,the reheated shell is delivered to the inlet table of a second piercingand expanding element 29. The piercing mill 29 is provided with inletand outlet tables longer than those customarily employed, to facilitatehandling the shell after a relatively heavy working effective toincrease the diameter and reduce the wall thickness. Because thetemperature of the shell is uniform throughout on leaving the furnace26, the working of the metal in the mill 29 may be effected with greateraccuracy and within the exacting tolerances re quired in this class ofwork. The wall thickness of the shell, for example, is substantiallyuniform along the entire length of the shell, as compared to thetapering wall section produced heretofore. The mill. 29 accomplishesmuch of the work which has previously been performed in the plug milland may even be adjusted to reduce the pipe substantially to thefinished size so that no rolling in the plug mill is required.

From the outlet table of the mill 29 indicated at .30, the shell isdischarged across skids 3| to a conveyor 32. The latter charges theshell into a second reheating furnace 33, if reheating is necessary.From the furnace 33, the shell is delivered to a run out conveyor 34 andthence across skids 35 to the receiving table 36 of a plug millindicated diagrammatically at 31. If reheating before plug rolling isnot necessary, the shell is discharged from the conveyor 32 across skids38 directly to the conveyor 34 and the skids 35.

After plug rolling, if required, the usual finishing operations such asreeling and sizing may be performed on the shell by apparatus well knownin the art.

A typical example of the practice of the invention described herein isthe manufacture of 10% outside diameter pipe having a wall thickness of.218". In this example, the double length billet is 8 /4" in diameter by13' 1.39" long and is cut in two after heating. After the firstpiercing, the outside diameter is 9 /2 with a wall thickness of .750"and the length 1 After the second piercing the shell is 11%;" indiameter with a wall thickness of .297" and the length is 34 8%" long.The plug rolling produces a pipe 10%" in diameter with a .233" wall, 47'long.

The wall thickness is reduced to .218" by conventional reeling andsizing operations. From the foregoing it will be seen that the plugrolling effects a reduction in the wall thickness of only .064". Thisreduction may be as high as .180" for certain grades of steel on certaindimensions of pipe and, as stated above, may be entirely eliminated forother grades of steel on certain dimensions of pipeand, as stated above,may be entirely eliminated for other grades and sizes.

It will be apparent from the foregoing description that the invention ischaracterized by numerous advantages over the method previously used inthe manufacture of seamless tubes. Most of these advantages have alreadybeen mentioned. They include the avoidance of cracking and rough surfaceconditions produced by a difference in the rate of cooling between theinner and outer surfaces of the shell, the ability to meet exactingtolerances as to wall thickness, the possibility of effecting most ofthe reduction in the second piercing mill, and the possibility ofutilizing a walking beam furnace which is readily subject to automaticcontrol. Secondary advantages are the possibility of eliminating plugrolling and economy and efficiency in the manufacture. of thin walled,large diameter pipe having a high uniformity of wall thickness. It willbe understood that although I have disclosed conventiona1 finishingprocedure, viz., reeling, sizing, etc., variations may be introducedtherein. By effecting the heavy reduction in the second piercing millinstead of the plug mill, I avoid the adverse effect of the latter uponthe condition of the inner surface of the shell.

I have illustrated and described but a preferred embodiment and practiceof the invention, but 6 changes therein may be made without departingfrom the spirit of the invention or the scope of the appended claims.

I claim:

1. In a method of making seamless tubes the steps including heating abillet to a temperature suitable for piercing, subjecting the heatedbillet to a piercing operation, thereby creating a temperaturedifferential between the leading and trailing ends of the resultingshell, subjecting the shell to a second piercing to reduce its wallthickness, and substantially preventing a progressive decrease in thewall thickness from the leading end toward the trailing end of the shellby supplying heat to the shell before the second piercing.

2. In a method of making seamless tubes the steps including heating abillet to a temperature suitable for piercing, subjecting the heatedbillet to a piercing operation, thereby creating a temperaturedifferential between the leading and trailing ends of the resultingshell, subjecting the shell to a second piercing to reduce its wallthickness, and substantially preventing a progressive decrease in thewall thickness from the leading end toward the trailing end of the shellby substantially equalizing the temperature of the oncepierced shellalong the entire length thereof before the second piercing.

3. In a method of making seamless tubes the steps including heating abillet to a temperature suitable for piercing, subjecting the heatedbillet to a piercing operation, thereby creating a temperaturedifferential between the leading and trailing ends of the resultingshell, subjecting the shell to a second piercing to reduce its wallthickness, and substantially preventing a progressive decrease in thewall thickness from the leading end toward the trailing end of the shellby so reheating the once-pierced shell as substantially to eliminatesaid differential.

4. In a method of making seamless tubes the steps including heatingmultiple-length billet to a temperature suitable for piercing, severingthe billet into portions, subjecting one of the severed portions to apiercing operation, thereby creating a temperature differential betweenthe leading and trailing ends of the resulting shell, subjecting theshell to a second piercing to reduce its wall thickness, andsubstantially preventing a progressive decrease in the wall thicknessfrom the leading end toward the trailing end of the shell by supplyingheat to the shell before the 20 second piercing.

- JAMES L. MAUTHE.

